Last night I updated my cameras firmware from 1.2 to 2.0 after I read about the ISO 100 would be available for selection, pretty straight forward doing the two updates (1.2 - 1.4 then 1.4 to 2.0), after the update I did a little more research into it and found out a few details that helped with these test shots below.

ISO 200, 1/500sec, f/3.2

ISO 100, 1/250 sec, f/3.2

Not a whole lot of difference between the two above shots, the photo taken at ISO 100 is brighter across the frame which in turn causes clipping in the highlights, this you can see in all my test shots below, all are how the camera took them, only changes are cropping and re-saving.

Next two are 100% crops on the same part of the image to see the noise in the background, the second image at ISO 100 is much smoother so a little experimenting with settings to find a sweet spot for noise and exposure with little to no clipping will be the next thing to figure out.

ISO 200, 1/500sec, f/3.2

ISO 100, 1/250 sec, f/3.2

ISO 100, 1/100 sec, f/2.20

ISO 200, 1/200 sec, f/2.20

ISO 100, 1/40 sec, f/8

In this one the highlight clipping is extreme in the sky. Basically no information left,

Shot again with EV at -0.3 and got most of the cloud details back.

ISO 100, 1/60 sec, f/8

ISO 200, 1/100 sec, f/8

ISO 100, 1/40 sec, f/8

This one is quite interesting, it shows that when on ISO 100 (Low ISO) this building comes out quite a bit different to the ISO 200 photo below. In all photos there is a noticeable lightening in the dark areas and in turn over exposing in some highlights, very easy to see when the histogram is turned on when previewing images.

ISO 200, 1/125 sec, f/8

My testing was done without a tripod and I didn't lock the exposure settings between shots. But I can see real benefits have having a Low ISO option when Dynamic Range is not an issue (even if it is Bracketing for HDR should resolve this so you get the best of low noise and high DR). One thing I am looking forward to trying out is long exposures during daylight hours with my variable ND.